Linear actuators are used for performing linear adjustment actions. One example that, however, does not limit the scope of this invention, is the use in a machine tool as a disengaging unit that enables a tool to be exchanged in a tool holder in which the tool can be fixed.
Linear actuators are known in different structural forms as referenced, for example, in DE 20 2009 015 840 U1. A linear actuator is described there that is likewise used for actuating a tool holder. The linear actuator comprises an electric motor with a stator and rotor, wherein a threaded spindle is coupled with the rotor, consequently it is rotated by the rotor. The threaded spindle is part of a screw drive that is constructed there as a planetary rolling contact gear. This screw drive further comprises a nut that can be moved axially by the screw drive, wherein the nut is fixed in a rotation-proof manner by a corresponding anti-rotation device. An axially moveable piston rod that leads to the tool holder is coupled with the nut.
On one side, the spindle is supported by the screw drive, here, the planetary rolling contact gear, on the other side, that is, on the other side of the rotor, there are several angled-contact ball bearings that are used for radial and axial support. The structure of this linear actuator, however, is very complex and, in particular, intensive in terms of installation space.